For Finding the All Duplicate Values (Original & Duplicate Values)
=COUNTIF($B:$B,$B1)1

For Finding the First Original Value:-
=IF(COUNTIF($B:$B,$B1)1,COUNTIF($B$1:$B1,$B1)=1)

For finding the Duplicate Values Apart from Original Values:-
=IF(COUNTIF($B:$B,$B6)1,COUNTIF($B$1:$B6,$B6)1)

1. Place the cursor in A1 and select the Entire Column (i.e.) A Column (if
you want to highlight only the A Column then Place the cursor in A1 Cell and
Select A Column, Otherwise select the Multiple columns, but the when
applying the conditional formatting the (active cell) cursor should be in 1st
cell of any Column)

2. From menu FormatConditional Formatting
3. For Condition1Select 'Formula Is' and enter the above codes whichever
you require.
4. Click Format ButtonFontColor select 'red' then give ok

You can change the Formula refence B column to your desired Column.

If this post helps, Click Yes!

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(MS-Exl-Learner)
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"Texas10" wrote:

How can I have a cell be highlighted at the beginning of a certain event?
Here's my example, I have 2 columns and in the right column it's a bunch of
numbers. The numbers are all different but there comes a point when they
start to repeat and I want excel to recognize the repeating cells and
highlight the cell to the left of the start of the repetition. Here's an
example because it's hard to explain, 2 columns and I'll just call one
letters and the other is numbers:
A 2
B 5
C 3
D 8
E 7
F 7
G 7
H 7

So I want it to highlight the cell called E here since it's the start of the
repetition. Any help would be greatly appreciated.